Preparative separation chromatograph system

ABSTRACT

A preparative separation chromatograph system having a column for temporally separating components in a sample and for discharging an eluate fluid with the components, a detector for obtaining an absorbance spectrum of the eluate fluid, and a fraction collector for continuously creating a chromatogram. The system further includes: a peak section determiner; a differential value determiner for calculating a differential spectrum value and for determining whether or not the absolute value of the differential spectrum value is equal to or less than a predetermined value; and a fraction collector controller for controlling the fraction collector so as to fractionate the eluate fluid during a period of time for which it is determined that the chromatogram peak of the target component is present and for which it is also determined the absolute value of the differential spectrum value is equal to or less than the predetermined value.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a National Stage of International Application No.PCT/JP2013/055852 filed Mar. 4, 2013, the contents of which areincorporated herein by reference in its entirety.

TECHNICAL FIELD

The present invention relates to a preparative separation chromatographsystem for separately collecting a specific component of a liquid or gaswhich has been separated from a liquid or gas sample by a column.

BACKGROUND ART

A so-called preparative separation chromatograph system for separatelycollecting one or more components contained in a sample using a liquidchromatograph or gas chromatograph has been commonly known. In thosekinds of preparative separation chromatograph systems, an eluate fluiddischarged from a column is fractionated and collected for a specificperiod of time by a fraction collector based on the retention time ofeach specific target component in the sample so as to isolate an eluatefluid containing that target component from the sample. The timing ofseparately collecting the eluate fluid containing the target componentin such a preparative separation chromatograph system is determined by amanual or automatic process.

If a comparatively large amount of sample is available, it is possibleto perform a preliminary chromatographic analysis for that sample tocreate a chromatogram and allow an operator to examine the chromatogramand determine the timing of fractionation. However, for example, ifthere is only a small amount of sample available or the sample isexpensive and valuable, it is impossible to perform the preliminarychromatographic analysis, and the fractionation must be performed with asingle chromatographic analysis.

Patent Literature 1 discloses a preparative separation chromatographsystem which concurrently performs two modes of fractionations: atime-based fractionation, in which the operation of discontinuing onefractionation and proceeding to the next one is repeated atpredetermined intervals of time, and a fractionation based on the peakdetection, in which, when the beginning point of a chromatogram peak isdetected, a fractionation for that peak is initiated, and when theending point of that peak is detected, the fractionation is discontinuedto proceed on to the next one. With this system, the component whosepeak has been detected can be assuredly isolated by the fractionation,while other trace amounts of components whose peaks are undetectable canalso be caught by one of the time-based fractionations performed anumber of times.

CITATION LIST Patent Literature

-   Patent Literature 1: JP 2010-014559 A

SUMMARY OF INVENTION Technical Problem

By the previously described fractionation, the target component can beseparately collected with a high degree of purity if the retention timesof the various components in the sample are sufficiently separated fromeach other. However, in a sample which contains various components, itis often the case that a different component (impurity) having aretention time considerably close to that of the target component iscontained. In such a case, the peaks of a plurality of components willoverlap, causing an impurity other than the target component to be mixedin the fractionated eluate fluid.

The problem to be solved by the present invention is to provide apreparative separation chromatograph system capable of separatelycollecting a target component with no impurity mixed even if a differentcomponent (impurity) having a retention time close to that of the targetcomponent is contained.

Solution to Problem

A preparative separation chromatograph system according to the presentinvention developed for solving the previously described problem is apreparative separation chromatograph system having a column fortemporally separating components in a sample and for discharging aneluate fluid with the components, a detector for obtaining an absorbancespectrum A(λ) of the eluate fluid, and a fraction collector forcontinuously creating a chromatogram S(t) in real time based on theabsorbance spectrum A(λ) and for fractionating the eluate fluid based onthe chromatogram S(t) to separately collect a target component, thesystem further including:

a) a peak section determiner for determining whether or not achromatogram peak of the target component is present based on thechromatogram S(t);

b) a differential value determiner for calculating a differentialspectrum value A′(λ₀)=d(A(λ))/dλ|_(λ=λ0) which is the value of awavelength differential d(A(λ))/dλ of the absorbance spectrum A(λ) at aknown wavelength λ₀ at which the absorbance of the target component hasa local maximum or local minimum value, and for determining whether ornot the absolute value of the differential spectrum value A′(λ₀) isequal to or less than a predetermined value; and

c) a fraction collector controller for controlling the fractioncollector so as to fractionate the eluate fluid during a period of timefor which it is determined that the chromatogram peak of the targetcomponent is present and for which it is also determined the absolutevalue of the differential spectrum value A′(λ₀) is equal to or less thanthe predetermined value.

In the preparative separation chromatograph system according to thepresent invention, the peak section determiner sequentially determineswhether or not a chromatogram peak corresponding to a target componentis present based on a chromatogram S(t) which is created in real time.The “real time” does not always mean that the chromatogram S(t) iscreated simultaneously with the acquisition of the absorbance spectrumA(λ) but allows for some amount of time as long as it does not hinderthe fractionation. The chromatogram S(t) may be either created based onan absorbance A(λ_(i))) at a specific wavelength λ_(i) within the peakof the absorbance spectrum corresponding to the target component, orbased on an integral of the absorbance spectrum A(λ) with respect to thewavelength λ. From the viewpoint of the data-processing load, it ispreferable to create the chromatogram S(t) based on the absorbanceA(λ_(i)) at a specific wavelength λ_(i). Whether or not a peakcorresponding to the target component in the chromatogram S(t) ispresent can be determined by a conventionally used method; for example,as described in Patent Literature 1, the determination at a point intime t=t_(a) may be made based on whether or not S(t_(a)) exceeds apredetermined threshold, or whether or not the slope of the curve S(t)at t=t_(a) exceeds a predetermined value.

Every time an absorbance spectrum A(λ) is obtained, the differentialvalue determiner calculates the differential spectrum value A′(λ₀) atthe aforementioned wavelength λ₀ (which is hereinafter called the“absorption extremal wavelength”) and sequentially determines whether ornot the absolute value of the differential spectrum value A′(λ₀) isequal to or less than a predetermined value. The frequency of theacquisition of the absorbance spectrum A(λ) for this determination maybe equal to that of the acquisition of the absorbance spectrum A(λ) forthe creation of the chromatogram S(t) or lower than that. The absorptionextremal wavelength λ₀ is a wavelength at which the absorbance of thetarget component has a local maximum or local minimum value. Thiswavelength changes depending on the target component. It should be notedthat, since common samples tend to have higher values of absorbance atshorter wavelengths, the absorbance of the target component may have thelocal minimum value in addition to the local maximum value. Forsimplicity, the following description mainly deals with the case wherethe absorbance has the local maximum value at the absorption extremalwavelength λ₀. The description will also similarly apply in the casewhere the absorbance has the local minimum value.

At a certain point in time, if no impurity is contained in the eluatefluid, no spectrum due to a component other than the target component issuperposed on the absorbance spectrum A(λ), so that the differentialspectrum value A′(λ₀) will ideally be zero. Actually, it is necessary toallow for the influences of measurement errors and other factors.Therefore, it is possible to consider that no impurity is contained inthe eluate fluid if the absolute value of A′(λ₀) is within a certainrange (i.e. equal to or less than the predetermined value). On the otherhand, if an impurity is contained in the eluate fluid, a spectrum due tothat impurity is superposed on the spectrum due to the target component,so that the absolute value of the differential spectrum value A′(λ₀)becomes greater than the predetermined value. Therefore, sequentiallydetermining whether or not the absolute value of the differentialspectrum value A′(λ₀) is equal to or less than the predetermined valuemeans determining whether or not an impurity is contained in the eluatefluid at each point in time. Thus, according to the present invention,whether or not an impurity is present can be determined even if animpurity having a retention time close to that of the target componenthinders isolation of the chromatogram peak concerned.

The fraction collector controller controls the fraction collector so asto fractionate the eluate fluid during a period of time for which thepeak section determiner has determined that the chromatogram peak of thetarget component is present, and for which the differential valuedeterminer has determined that the absolute value of the differentialspectrum value A′(λ₀) is equal to or less than the predetermined value(i.e. that the eluate fluid does not contain any impurity). By thiscontrol, the target component with no impurity contained can beseparately collected.

As noted earlier, common samples tend to have higher values ofabsorbance at shorter wavelengths. Therefore, in the case of creating achromatogram S(t) based on the absorbance A(λ_(i)) at a specificwavelength λ_(i), the specific wavelength λ_(i) should preferably be,but not limited to, a wavelength shorter than the absorption extremalwavelength λ₀ of the target component.

In the present invention, the chromatograph may be either a liquidchromatograph or gas chromatograph. As the detector, a multichanneldetector capable of simultaneously detecting a number of wavelengths istypically used, such as a photodiode array. It is also possible to usean ultraviolet-visible spectrophotometer, infrared spectrophotometer,near-infrared spectrophotometer, fluorescence spectrophotometer or otherspectrophotometers which perform a wavelength scan.

Instead of determining whether or not the differential spectrum valueA′(λ₀) at the wavelength λ₀ is equal to zero, the differential valuedeterminer may find the wavelength λ_(a) at which the wavelengthdifferential d(A(λ))/dλ of the absorbance spectrum A(λ) has a value ofzero, and determine whether or not this wavelength coincides with λ₀. Ifλ_(a)=λ₀, it means that no impurity is contained in the eluate fluid.Similarly to the previous case, it is actually necessary to allow forthe influences of measurement errors and other factors, and therefore,it is possible to consider that no impurity is contained in the eluatefluid if the absolute value of the difference between λ_(a) and λ₀ isequal to or less than a predetermined value. Conversely, if the absolutevalue of the difference between λ_(a) and λ₀ is greater than thepredetermined value, it means that an impurity is contained in theeluate fluid.

Thus, a preparative separation chromatograph system having such adifferential value determiner is also provided, which is a preparativeseparation chromatograph system having a column for temporallyseparating components in a sample and for discharging an eluate fluidwith the components, a detector for obtaining an absorbance spectrumA(λ) of the eluate fluid, and a fraction collector for continuouslycreating a chromatogram S(t) in real time based on the absorbancespectrum A(λ) and for fractionating the eluate fluid based on thechromatogram S(t) to separately collect a target component, the systemfurther including:

a) a peak section determiner for determining whether or not achromatogram peak of the target component is present based on thechromatogram S(t);

b) a differential value determiner for finding a wavelength λ_(a) atwhich the value of a wavelength differential d(A(λ))/dλ of theabsorbance spectrum A(λ) becomes zero, and for determining whether theabsolute value of the difference between the wavelength λ_(a) and aknown wavelength λ₀ at which the absorbance of the target component hasa local maximum or local minimum value is equal to or less than apredetermined value; and

c) a fraction collector controller for controlling the fractioncollector so as to fractionate the eluate fluid during a period of timefor which it is determined that the chromatogram peak of the targetcomponent is present and for which it is also determined that theabsolute value of the difference between the wavelengths λ_(a) and λ₀ isequal to or less than the predetermined value.

Advantageous Effects of the Invention

With the preparative separation chromatograph system according to thepresent invention, it is possible to separately collect a targetcomponent with no impurity mixed even if a different component(impurity) having a retention time close to that of the target componentis contained.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic configuration diagram of a preparative separationLC system as one embodiment of the preparative separation chromatographsystem according to the present invention.

FIG. 2A is a model diagram of an absorbance spectrum A(λ) and FIG. 2B isa model diagram of a chromatogram S(t) obtained from the absorbancespectrum A(λ).

FIG. 3 is a diagram showing one example of an absorbance of a targetcomponent x and that of an impurity component y separated from eachother.

FIG. 4 is a diagram showing a peak profile of the target component x,that of the impurity component y, and a mixed peak profile of the twopeak profiles on a chromatogram, with the indications of the sections ofelution of the target component x and impurity component y, as well asthe section for the preparative separation of the target component x bythe preparative separation chromatograph system of the presentembodiment.

FIG. 5 is a diagram showing a differential spectrum obtained bydifferentiating the absorbance spectrum of each of the target andimpurity components x and y with respect to the wavelength.

FIG. 6 is a flowchart showing an operation of the preparative separationchromatograph system of the present embodiment.

FIG. 7 is a flowchart showing an operation of one variation of thepreparative separation chromatograph system.

DESCRIPTION OF EMBODIMENTS

One embodiment of the preparative separation chromatograph systemaccording to the present is described using FIGS. 1-7.

EMBODIMENTS (1) Configuration of Preparative Separation ChromatographSystem of Present Embodiment

The preparative separation chromatograph system of the presentembodiment is a preparative separation LC system using a liquidchromatograph (LC). As shown in FIG. 1, the preparative separation LCsystem 10 includes a mobile phase container 11, liquid-sending pump 12,injector 13, column 14, detector 15 and fraction collector 16, which areconnected by a liquid-sending passage 19 in the above-mentioned order.The preparative separation LC system 10 also has a control unit 17 forcontrolling the fraction collector 16 based on the data obtained fromthe detector 15.

In the preparative separation LC system 10, a mobile phase held in themobile phase container 11 is drawn by the liquid-sending pump 12 andpassed through the injector 13 into the column 14 at a fixed flow rate.In the injector 13, a sample is injected into the mobile phase. Thesample is carried by the mobile phase into the column 14 and iseventually discharged from this column 14 after being temporallyseparated while passing though the column 14. The detector 15 in thepresent embodiment is an ultraviolet spectrophotometer having anultraviolet light source 151, a flow cell 152 through which an eluateflows, a light-dispersing device 153 including a diffraction grating andother elements, a photodiode array 154 and an absorbance spectrumcreator 155. Measurement light emitted from the ultraviolet light source151 travels through the eluate flowing through the flow cell 152, wherethe light undergoes absorption at wavelengths characteristic of thecomponents contained in the eluate. The transmitted light is dispersedinto component wavelengths by the light-dispersing device 153. Thedispersed wavelengths of light within a measurement range aresimultaneously detected by the photodiode array 154. As a result, aspectrum I(λ) showing the signal intensity at each wavelength of thetransmitted light is obtained. In the absorbance spectrum creator 155,the signal-intensity spectrum I₀(λ) obtained at the beginning of theanalysis is stored in a memory unit. After that, an absorbance spectrumA(λ)=log(I₀(λ)/I(λ)) is calculated from the continuously obtainedsignal-intensity spectrum I(λ). The detector 15 outputs a signalrepresenting this spectrum.

The eluate which has passed through the detector 15 is entirely (or maybe partially) introduced into the fraction collector 16. The fractioncollector 16 has a solenoid valve 161, a container rack 162 for holdinga number of containers, a dispensing nozzle 163 provided on thedownstream side of the solenoid valve 161 for dropping the eluate, and adrive unit 164 for moving the dispensing nozzle 163 in two axialdirections so as to change the container to be used for collecting theeluate. The open/close operation of the solenoid valve 161 and themovement of the dispensing nozzle 163 by the drive unit 164 arecontrolled by a control unit 17 (which will be described later).

The control unit 17 has a peak section determiner 171, differentialvalue determiner 172 and fraction collector controller 173. It isembodied by a CPU and software.

The peak section determiner 171 obtains the absorbance spectrum A(λ)from the detector 15, creates a chromatogram S(t) in real time based onthe absorbance spectrum A(λ), and continuously determines whether or nota chromatogram peak corresponding to the target component is present. Inthe present embodiment, if the point in time of determination, t=t_(a),is within a predetermined range of time including a (known) retentiontime of the target component and if S(t_(a)) exceeds a threshold, it isdetermined that a chromatogram peak corresponding to the targetcomponent is present. Meanwhile, every time one set of signals of theabsorbance spectrum A(λ) is obtained from the detector 15, thedifferential value determiner 172 sequentially calculates thedifferential spectrum value A′(λ₀) at the known absorption extremalwavelength λ₀ and sequentially determines whether or not thedifferential spectrum value A′(λ₀) is zero.

The fraction collector controller 173 controls the fraction collector 16so as to fractionate the eluate fluid during a period of time for whichit is determined by the peak section determiner 171 that a chromatogrampeak is present and for which it is also determined by the differentialvalue determined 172 that the differential spectrum value A′(λ₀) iszero. Specifically, before those determinations are made, the fractioncollector controller 173 moves the dispensing nozzle 163 to a positionabove a container to be used for separately collecting the targetcomponent, and when those determinations have been made, it performs acontrol for opening the solenoid valve 161. After that, when it is foundthat the conditions for those determinations are no longer satisfied,the fraction collector controller 173 performs a control for closing thesolenoid valve 161.

(2) Principle of Determination on Presence of Impurity in Eluate Fluid

The principle of determining whether or not an impurity is present in aneluate fluid by processing data in the differential value determined 172of the preparative separation LC system 10 of the present embodiment isdescribed using FIGS. 2-5.

FIG. 2A is a model diagram of three-dimensional chromatogram data havingthe three dimensions of time t, wavelength λ and absorbance A. Among thethree-dimensional chromatogram data, the relationship between absorbanceS and wavelength λ at a specific time t=t_(a) corresponds to theabsorbance spectrum A(λ) at that time t (the curves in FIG. 2A).Furthermore, in the present embodiment, the relationship betweenabsorbance S and time t at a specific wavelength λ=λ_(i) corresponds tothe chromatogram S(t) at that wavelength λ_(i) (FIG. 2B). According tothe present embodiment, whether or not an impurity is present isdetermined as follows using the absorbance spectrum A(λ).

Consider the case where a target component x and impurity component yare contained as two components in a sample. FIG. 3 shows one example ofthe absorbance spectrum of the target component x and that of theimpurity component y separated from each other. As can be seen, ingeneral, each substance has a different wavelength corresponding to thetop (local maximum point) of the absorbance peak (absorption localmaximum wavelength). Furthermore, since the absorbance tends to behigher at shorter wavelengths, a negative peak (local minimum point) mayappear at a shorter wavelength than the local maximum point in theabsorbance spectrum.

FIG. 4 shows one example of the peak profile of each of the target andimpurity components x and y on a chromatogram as well as a mixed peakprofile, i.e. the superposition of the two peak profiles. A chromatogramactually obtained from an absorbance spectrum being measured is themixed peak profile. Since the retention time of the target component xis considerably close to that of the impurity component y, it difficultto determine, from the mixed peak profile, the period of time withinwhich the impurity is mixed in the eluate fluid.

Accordingly, in the present embodiment, a differential spectrum obtainedby differentiating the absorbance spectrum with respect to wavelength isused in a manner to be hereinafter described in order to determinewhether or not the impurity component y is mixed. FIG. 5 showsdifferential spectra obtained by differentiating the absorption spectrumof each component shown in FIG. 3 with respect to wavelength. Thedifferential spectrum has a positive value in a phase where the curve ofthe wavelength spectrum is rising with the wavelength, a negative valuein a phase where the curve is falling, and zero at local maximum andlocal minimum points of an absorbance peak. In the present embodiment,the absorption local maximum wavelength of the target component x, i.e.the wavelength at which the differential spectrum becomes zero duringthe transition from positive to negative values, is defined as λ₀.

As noted earlier, in general, each substance has a different absorptionlocal maximum wavelength. Accordingly, as shown, the absorption localmaximum wavelength of the impurity component y is different from theabsorption local maximum wavelength λ₀ of the target component x.Furthermore, the differential spectrum of the impurity component y has anon-zero value at the absorption local maximum wavelength λ₀ of thetarget component x. Therefore, if the eluate fluid contains only thetarget component x (i.e. if it does not contain the impurity componenty), the differential spectrum value measured at the absorption localmaximum wavelength λ₀ will ideally be zero. On the other hand, if theeluate fluid contains the impurity component y in addition to the targetcomponent x, the differential spectrum value measured at the absorptionlocal maximum wavelength λ₀ will be a non-zero value.

Accordingly, in the present embodiment, the differential spectrum valueA′(λ₀) at the absorption local maximum wavelength λ₀ is calculatedsequentially (at each point in time), and whether or not thedifferential spectrum value A′(λ₀) is zero is determined to judgewhether the eluate fluid contains an impurity component y (A′(λ₀)≠0) ornot (A′(λ₀)=0) at that point in time. It is also possible to determinethat the eluate fluid does not contain any impurity component y at thatpoint in time if the absolute value of the differential spectrum valueA′(λ₀) is within a certain range, taking into account the influences ofmeasurement errors and other factors. According to such a determinationmethod, the system of the present embodiment performs the separatecollection of the target component x only within the period of timeduring which the eluate fluid does not contain any impurity component y(the “section for preparative separation” in FIG. 4).

The description thus far has dealt with the case of using the wavelengthcorresponding to the local maximum point of the absorbance peak as theabsorption local maximum wavelength. It is also possible to similarlyuse the absorption local minimum wavelength, i.e. the wavelength whichcorresponds to the local minimum point of the absorbance peak.

(3) Operation Flow of Preparative Separation Chromatograph System ofPresent Embodiment

An operation flow of the preparative separation LC system 10 of thepresent embodiment is described using the flowchart of FIG. 6. Thepreparative separation LC system 10 repeats the sequence of Steps S1through S7 until a condition in Step S7 is satisfied. One loop of thisrepetitive operation is hereinafter described.

Initially, the peak section determiner 171 obtains an absorbancespectrum A(λ) from the detector 15 (Step S1), and renews thechromatogram S(t) for the present point in time (t=t_(a)) by obtainingthe absorbance for λ=λ_(i) at t=t_(a) and adding it to the previouslyobtained chromatogram S(t) as S(t_(a)), i.e. the value of chromatogramS(t) at t_(a) (Step S2). Subsequently, based on the obtained S(t), thepeak section determiner 171 applies the previously described method todetermine whether or not the present point in time is within the peakperiod of the target component (Step S3). If the present point in timeis within the peak period of the target component, the operationproceeds to Step S4. If the present point in time is not within the peakperiod of the target component, the system returns to Step S1 and oncemore performs the previously described operations through to Step S3.

Next, based on the presently obtained absorbance spectrum A(λ), thedifferential value determiner 172 calculates the differential spectrumvalue A′(λ₀) at the absorption local maximum wavelength (or absorptionlocal minimum wavelength) λ₀ (Step S4), and determines whether or notthe differential spectrum value A′ (λ₀) is zero (Step S5).

In Step S5, if it is determined that the differential spectrum valueA′(λ₀) is zero, the operation proceeds to Step S6-1, where the fractioncollector controller 173 performs the previously described operation forseparately collecting the eluate as the solution of the targetcomponent. In the case where this operation for the separate collectionhas already been executed in the previous loops, the operation is simplymaintained in Step S6-1. After Step S6-1 is completed, the operationproceeds to Step S7.

On the other hand, in Step S5, if it is determined that the differentialspectrum value A′(λ₀) is not zero, the operation proceeds to Step S6-2.In Step S6-2, the fraction collector 173 performs a necessary operationfor preventing the eluate from being separately collected as thesolution of the target component. That is to say, if the preparativeseparation is presently underway, the solenoid valve 161 should beclosed, or if the preparative separation is not underway, the same stateis maintained. After Step S6-2 is completed, the operation proceeds toStep S7.

In Step S7, whether or not a predetermined amount of time has elapsedsince the beginning of the operation is determined. If the kind oftarget component is known, the amount of time required for thatcomponent to be completely eluted from the column is also known, so thatthis amount of time can be chosen as the predetermined amount of time.If the predetermined amount of time has not yet elapsed, the systemreturns to Step S1 and once more performs the previously describedoperations. If the predetermined amount of time has elapsed, the entireoperation is completed.

(4) First Variation

The present invention is not limited to the previous embodiment.

In the previous embodiment, the differential value determiner 172 isconfigured to determine whether or not the differential spectrum valueA′(λ₀) at the absorption local maximum wavelength λ₀ is zero.Alternatively, the determination may be made as follows:

As noted earlier, in general, the absorption local maximum wavelength(or absorption local minimum wavelength; which is hereinafter the same)of an impurity component y is different from the absorption localmaximum wavelength λ₀ of a target component x (FIG. 5). Therefore, ifthe eluate fluid contains only the target component x (i.e. if it doesnot contain the impurity component y), the value of the wavelengthdifferential A′(λ)=d(A(λ))/dλ of the absorption spectrum A(λ) of theeluate fluid will be zero at the absorption local maximum wavelength λ₀.On the other hand, if the eluate fluid contains the impurity component yin addition to the target component x, A′(λ) of the eluate fluid will bezero at a wavelength different from λ₀.

Accordingly, as shown in FIG. 7, the differential value determiner 172may be configured to find the wavelength λ_(a) at which the value of thewavelength differential A′(λ) of the absorbance spectrum A(λ) becomeszero (Step S4A), and determine whether or not this wavelength λ_(a)coincides with λ₀ (Step S5A). If wavelength λ_(a) coincides with λ₀, thepreviously described Step 6-1 is performed, or if wavelength λ_(a) doesnot coincide with λ₀, the previously described Step 6-2 is performed. Itis also possible to perform Step 6-1 if the absolute value of thedifference between the wavelengths λ_(a) and λ₀ is within a certainrange, taking into account the influences of measurement errors andother factors.

(5) Other Variations

In the previous embodiment, in place of the ultravioletspectrophotometer having a photodiode array, an ultravioletspectrophotometer which performs a wavelength scan may be used as thedetector 15, in which case the wavelength spectrum cannot besimultaneously obtained, since a certain amount of time is required forthe scan. A different type of detector may also be used as the detector15, such as an infrared spectrophotometric detector orspectrofluorometric detector.

Although the previously described embodiment is a preparative separationliquid chromatograph system, a similar configuration can also be adoptedin the case of a gas chromatograph for analyzing a gas sample. In thecase of a gas chromatograph, an infrared spectrophotometer ornear-infrared spectrophotometer should preferably be used as thedetector 15.

REFERENCE SIGNS LIST

-   10 . . . Preparative Separation LC System-   11 . . . Mobile Phase Container-   12 . . . Liquid-Sending Pump-   13 . . . Injector-   14 . . . Column-   15 . . . Detector-   151 . . . Ultraviolet Light Source-   152 . . . Flow Cell-   153 . . . Light-Dispersing Device-   154 . . . Photodiode Array-   155 . . . Absorbance Spectrum Creator-   16 . . . Fraction Collector-   161 . . . Solenoid Valve-   162 . . . Container Rack-   163 . . . Dispensing Nozzle-   164 . . . Drive Unit-   17 . . . Control Unit-   171 . . . Peak Section Determiner-   172 . . . Differential Value Determiner-   173 . . . Fraction Collector Controller-   19 . . . Liquid-Sending Passage

The invention claimed is:
 1. A preparative separation chromatographsystem having a column for temporally separating components in a sampleand for discharging an eluate fluid with the components, a detector forobtaining an absorbance spectrum A(λ) of the eluate fluid, and afraction collector for continuously creating a chromatogram S(t) in realtime based on the absorbance spectrum A(λ) and for fractionating theeluate fluid based on the chromatogram S(t) to separately collect atarget component, the system further comprising: a) a peak sectiondeterminer for determining whether or not a chromatogram peak of thetarget component is present based on the chromatogram S(t); b) adifferential value determiner for calculating a differential spectrumvalue A′(λ₀)=d(A(λ))/dλ|_(λ=λ0) which is a value of a wavelengthdifferential d(A(λ))/dλ of the absorbance spectrum A(λ) at a knownwavelength λ₀ at which an absorbance of the target component has a localmaximum or local minimum value, and for determining whether or not anabsolute value of the differential spectrum value A′(λ₀) is equal to orless than a predetermined value; and c) a fraction collector controllerfor controlling the fraction collector so as to fractionate the eluatefluid during a period of time for which it is determined that thechromatogram peak of the target component is present and for which it isalso determined the absolute value of the differential spectrum valueA′(λ₀) is equal to or less than the predetermined value.
 2. Apreparative separation chromatograph system having a column fortemporally separating components in a sample and for discharging aneluate fluid with the components, a detector for obtaining an absorbancespectrum A(λ) of the eluate fluid, and a fraction collector forcontinuously creating a chromatogram S(t) in real time based on theabsorbance spectrum A(λ) and for fractionating the eluate fluid based onthe chromatogram S(t) to separately collect a target component, thesystem further comprising: a) a peak section determiner for determiningwhether or not a chromatogram peak of the target component is presentbased on the chromatogram S(t); b) a differential value determiner forfinding a wavelength λ_(a) at which a value of a wavelength differentiald(A(λ))/dλ of the absorbance spectrum A(λ) becomes zero, and fordetermining whether an absolute value of a difference between thewavelength λ_(a) and a known wavelength λ₀ at which an absorbance of thetarget component has a local maximum or local minimum value is equal toor less than a predetermined value; and c) a fraction collectorcontroller for controlling the fraction collector so as to fractionatethe eluate fluid during a period of time for which it is determined thatthe chromatogram peak of the target component is present and for whichit is also determined that the absolute value of the difference betweenthe wavelengths λ_(a) and λ₀ is equal to or less than the predeterminedvalue.
 3. The preparative separation chromatograph system according toclaim 1, wherein the chromatogram S(t) is created based on an absorbanceA(λ_(i)) at a specific wavelength λ_(i) within the peak of theabsorbance spectrum corresponding the target component.
 4. Thepreparative separation chromatograph system according to claim 3,wherein the wavelength λ_(i) is shorter than the wavelength λ₀.
 5. Thepreparative separation chromatograph system according to claim 2,wherein the chromatogram S(t) is created based on an absorbance A(λ_(i))at a specific wavelength λ_(i) within the peak of the absorbancespectrum corresponding the target component.
 6. The preparativeseparation chromatograph system according to claim 5, wherein thewavelength λ_(i) is shorter than the wavelength λ₀.